Direct nitration of 2-aminobenzothiazoles substituted in the 6-position leads to a mixture of 2-amino-4-nitro- and 2-amino-5-nitrothiazoles (EP 374,041).
It is also known to prepare 4-, 5-, 6- or 7-nitro-2-aminobenzothiazoles by reacting dinitrochlorobenzenes or dinitrophenyl thiocyanates with thiourea or ammonium thiocyanate (U.S. Pat. No. 4,808,723, R. Hamprech, Chem. Abstr., 101, 211131 and J. Schulze et al., Z. Chem., 20, 436 (1980)); by reacting nitrophenylthioureas with S.sub.2 Cl.sub.2 or a lead(IV)-phosphate complex (S. Claude et al., Helv. Chim. Acta, 64, 1545 (1981); S. A. Von Mahmoud et al., Prakt. Chemie, 316, 154 (1974)). However, these cyclisations are not always regioselective.